[Elecraft] K2 No Power Output

[VA1CQ]

I've discovered that my VPWR voltage is high (4.90 V). I don't see 
anything wrong with the RF Detector circuit. The signal on D9 is only 84 
mV when measured with the RF Probe. So I pressed forward with signal 
tracing. It appears I have an RF signal at the Transmit Mixer (0.274 V) 
and Buffer (1.45 V) outputs. But at W6 (Band-Pass Filter output) and T-R 
Switch #1 output, I have no measurable signal (0.5 mV). Further, DC 
voltages check out on diodes D1 to D7 on the RF Board and all diodes are 
oriented correctly on the board. I also noted that the Driver and PA 
transistors have correct voltages and seem to switch on keydown.

Tuning the Band-Pass filters had no effect no effect on improving output 
power.  Power remains at 0.1 to 0.2 watts. I was able to tune L8 and L9 
for the 30-metre filter to improve reception on that band to receive 
some RTTY, WWV and a CW signal.

During the build, I swapped location of the two 20-metre trimmer 
capacitors (C21, C23) with the location for the 10-metre trimmers (C44, 
C46). In reversing these, it's possible I damaged one or more of the 
trimmers. But, if I did, I don't think this would cause the no power 
output problem on any band that I'm experiencing.

Murray VA1CQ


On 6/26/2021 6:33 PM, Don Wilhelm wrote:
> Murray,
>
> Not only logical, but the only way to approach Transmit problems.
> When you get to jumper W6, know that you can and should adjust the 
> bandpass filters for maximum RF voltage there.
>
> On a new build, be aware that the most common problems are soldering, 
> misplaced or incorrect components and diode orientation.  If you 
> suspect diode orientation problems, refer to the Parts Placement 
> Diagrams in the back of the manual to check them.
> Another common problem is inadequately stripped and tinned toroid 
> leads.  You should be able to see a bit of tinned lead on the top of 
> the board.
>
> 73,
> Don W3FPR
>
> On 6/26/2021 4:58 PM, VA1CQ wrote:
>> Don,
>>
>> A logical suggestion. I already have made the RF Probe and it's ready 
>> to use. I was hoping the cause of no power might be something 
>> simpler. I will start troubleshooting in my next work session.
>>
>> Murray VA1CQ
>>
>> On 6/26/2021 5:34 PM, Don Wilhelm wrote:
>>> Murray,
>>>
>>> I suggest that you build the RF Probe that was included with the K2 
>>> kit.  The schematic is shown on page 9 of Appendix E along with the 
>>> assembly instructions.
>>> After that, start on Appendix E page 12 - Preparation for 
>>> Transmitter Signal Tracing and follow the steps shown there.
>>>
>>> 73,
>>> Don W3FPR
>>>
>>> On 6/26/2021 4:21 PM, VA1CQ wrote:
>>>> I am just completing the build of K2 Serial No. 6397. Everything 
>>>> was going perfectly with all receiver tests and adjustments. 
>>>> Everything is in spec.
>>>>
>>>> Then I started the transmitter tests. I set the output power 
>>>> control for 2.0 watts. Beginning on 40 metres, I am supposed to be 
>>>> able to adjust L1 and L2 to measure 2 watts on the internal power 
>>>> meter. I measure 0.1 to 0.2 watts. Nothing I adjust or do changes 
>>>> this. My input voltage is 13.6V with 250 mA on receive and 600 mA 
>>>> on transmit. I've taken a quick read through the Troubleshooting 
>>>> section, but I'm wondering if I'm just doing something stupid and 
>>>> only think I have a problem when I don't. Being new to the K2, 
>>>> perhaps I'm not setting something correctly.
>>>>
>>>> Any tips for what I should do next?
>>>>
>>>> Murray VA1CQ
>>>>
>>>>
>>>
>>
>

-- 
This email has been checked for viruses by AVG.
https://www.avg.com